1. Field of the Invention
The present invention relates to an image communication device, and more particularly, to a data transmission protocol in an image communication device.
2. Discussion of Related Art
An image communication device based on a conventional technique is described referring to the accompanied drawings, as follows.
FIG. 1 represents a block diagram of an image communication device. The image communication device is composed of a semiconductor optical element such as a CCD(Charge Coupled Device) 1 for converting light inputted from the outside through a lens 1a into an electric image signal, a CCD driving part 2 for transferring the image signal inputted through the CCD 1 to a digital signal processor(DSP) 3, the digital signal processor 3 for performing a digital signal process on the image signal inputted from the CCD driving part 2, displaying and outputting the processed signal through a monitor 4, and outputting the processed signal as a format of a luminance signal and a color signal for the sake of a compression of the image, an image compression/decompression part 5 for compressing and decompressing the inputted image signals, a communication control and interface part 6 for executing a communication with a communication circuit and sound input/output part 8 in order to transmit the compressed image signal and receive the transmitted image signal, and a controlling part 7 for controlling the respective parts of the system to perform a process, a compression and decompression, a transmission, etc. of the image signals.
FIG. 2 sets forth a frame structure showing a data communication method which uses an HDLC(High-Level Data Link Control) way. This frame structure is made up of a start flag for informing of a start of a file, data information, e.g., audio/video/control/etc., a CRC(Cycle Redundancy Check) code as an error search code, and a stop flag for informing of a completion of the file.
FIG. 3 shows a frame structure of the data information based on a conventional non-protocol method.
Describing the image communication device based on the conventional technique with such construction in detail, referring to the accompanied drawings, outside light inputted through the lens 1a is converted into an electric image signal through the CCD 1, and is inputted to the CCD driving part 2. The CCD driving part 2 performs an analog signal correction for the image signal to make the signal a constant level, and outputs it to the DSP 3.
The DSP 3 executes a clamp, an RGB color control, a lightness control etc., for the inputted image signal, and then, displays the inputted image on the monitor 4.
At this time, the DSP 3 converts the inputted image into a constant format of a luminance signal and a color signal to gain an image compression in order for its transmission to the outside, and outputs it to the image compression/decompression part 5.
The image compression/decompression part 5 performs the image compression by the JPEG(Joint Photographic Coding Experts Group) and the MPEG(Moving Picture Experts Group) according to a kind of the inputted image signals, and such compressed image signal is transmitted to the communication circuit and sound input/output part 8 through the communication control and interface part 6.
A flow of this signal is controlled by the controlling part 7.
As the data communication method using a MODEM as the communication control and interface part 6 in such image communication device, there are an HDLC(High-Level Data Link Control) method and a non-protocol method, and the HDLC method is mainly used.
FIG. 2 provides a frame structure showing a data communication method which uses the HDLC way, and this frame structure includes a start flag for informing of a start of a file, data information, e.g., audio/video/control/etc., a CRC code as an error search code, and a stop flag for informing of a completion. In the HDLC structure, a flag pattern of the start and stop flags, xe2x80x9801111110(7EHEC)xe2x80x99, has a writing by a combination of 8 bit, wherein the start and stop flags are to inform of a start and a completion of a file for the sake of a synchronization of the frame.
That is, the flag synchronizing system is to send a code of a constant pattern and always attain a synchronization between the transmission and the reception even though there is no transmission data, and this constant pattern is as the flag pattern xe2x80x9801111110(7EHEC)xe2x80x99, the 7EHEC being a hexadecimal.
The MODEM of a receiving side which receives this flag, transfers the flag to the controlling part, CPU, under a removal state of the start and stop flags.
Data information sent, next to the start flag, contains optional bytes such as audio/video/control/etc. and is sent. Data 1 byte is herewith provided by a structure of 8 bit, and both ends of this 8 bit have each additional 1 bit as a start bit and a stop bit, thus 10 bit is transmitted.
The data information itself contains a CRC code in order to search the respective data such as the audio/video/control etc.
Six Data xe2x80x981sxe2x80x99 in the above data stream are limited to the flag (01111110). Therefore, when one data information to be sent needs over six consecutive xe2x80x981sxe2x80x99, xe2x80x980xe2x80x99 is compulsorily added next to fifth xe2x80x981xe2x80x99 as a zero insert, so that it is definitely divided with the start and stop flags. Then, the receiving side removes xe2x80x980xe2x80x99 positioned next to the fifth xe2x80x981xe2x80x99 of the consecutive xe2x80x981sxe2x80x99.
The CRC code, namely an error searching code, is provided next to this data stream, and this is as a combination of 16 bit and checks an existence or non-existence of an error for a part excepting the start and stop flags.
In such HDLC method, however, it is the state that the CRC code for a search of an error is already made in the data information such as the audio/video/control/etc., and that the repeated CRC code is then provided by using a MODEM line, to accordingly cause an overhead by an extent of a CRC code.
Further, a large overhead by data 1 byte, namely 10 bit, is transmitted to transmit the data 1 byte though data 1 byte is 8 bit, since each 1 bit as the start and stop bit is added in a data transmission. Consequently, a loss of a data quantity per communication second becomes large and its size also becomes increase.
Furthermore, when over six xe2x80x981sxe2x80x99 among data of the data information are consecutive, xe2x80x980xe2x80x99 is compulsively added next to a fifth xe2x80x981xe2x80x99 to prevent a restriction to the flag. In other words, xe2x80x980xe2x80x99 is inserted in order to prevent an existence of data same as the start and stop flags. Thus, an overhead of the data information owing to an insertion of xe2x80x980xe2x80x99 and a complication to again eliminate xe2x80x980xe2x80x99 by the receiving side are increased.
In the non-protocol method, meantime, as shown in FIG. 3, its structure is to directly transmit and receive sending data with only a data stream.
Then, the receiving side previously decides with a transmitting side a mutual protocol for a file division of an audio, a video, a control, etc. among the transmitted data information, and after that, a transmission from its protocol is performed, namely the protocol transmission for a xe2x80x98video:control=3:2xe2x80x99 etc. is executed. The receiving side has a difficulty in distinguishing it, and also, in a case of changing the transmission protocol and transmitting it within a given quantity, a newly dividing work is required every its each case.
Additionally, in the HDLC method mainly used as the conventional transmission method, several search codes of the data information and error search codes added in the MODEM transmission are repeated, thus an overhead by its added quantity occurs. Further, the overhead for the 1 byte data, the data loss and the size increase are caused, since the start and stop bits are added to the data 1 byte by each 1 bit. In addition, there are complicated problems such as the overhead caused due to a compulsive addition of xe2x80x980xe2x80x99 to the data information restricted to the flag, and its data removal performed by the receiving side, and there is a difficulty for distinguishing each data information by the receiving side.
Accordingly, the present invention is directed to a data transmission protocol of an image communication device that substantially obviate one or more of the limitations and disadvantages of the related art.
An object of the present invention is to provide a data transmission protocol of an image communication device, in which a transmission efficiency per unit time is heightened by eliminating overhead data in transmitting data through a MODEM, and a receiving side can easily execute a search of mutually different files/data packets to shorten a MODEM connection time.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure as illustrated in the written description and claims hereof, as well as the appended drawings.
To achieve these and other advantages, and in accordance with the purpose of the present invention as embodied and broadly described, the data transmission protocol of an image communication device transmits data under the structure of a flag for informing of a start of a file, header information for discriminating a nature of data information, flag data address information which contains address information corresponding to flag data of the data information, data information which contains the rest data excepting the flag data, and a flag for informing of a completion of the file.
The inventive data transmission protocol has another characteristic that in the flag for informing of the start and the completion, a flag pattern for the sake of a distinction between files is selected as one out of digits larger than xe2x80x981000000(80HEC)xe2x80x99, the flag pattern being as a combination of 8 bits.
In the flag for informing of the start and the completion according to the inventive protocol, a data usage range can be freely in xe2x80x9c0xcx9c7Fxe2x80x9d by using xe2x80x9810000001(81HEC)xe2x80x99 as a larger digit 128DEC.
In the header information for the inventive other characteristic, 8 bit is combined to distinct a nature of data as the audio/video/control/user/etc., and data is respectively represented as mutually different codes in order for an easy recognition of each data. Also, in a case of a transmission of the data information based on the same nature, a characteristic of files for the respective data information is subdivided and the data is transmitted by mutually different codes.
In the header information according to the inventive characteristic, 8 bit of the mutually different codes is combined so as to easily distinguish a nature of the mutually different data and files"" characteristic of the same data, and its codes can be respectively designated among digits larger than 80HEC.
In the flag data address information according to the inventive characteristic, in case that there is data same as the flag data among data of the data information, an address pointer for its respective data is combined by 8 bit to attain consecutively optional bytes.
In the flag data address information according to the inventive characteristic, in case that there is data same as xe2x80x9810000001xe2x80x99 among data of the data information, an address pointer for its respective data is combined by 8 bit to gain consecutively optional bytes.
In the data information according to the inventive characteristic, only the rest data excepting the data same as the flag data is sent.
In the data information according to the inventive characteristic, only the rest data excepting the data same as the flag data xe2x80x9810000001xe2x80x99 is transmitted, and if positional information of the respective data is over xe2x80x9801111111(7FHEC)xe2x80x99 as a threshold, an identifier as xe2x80x9811110000(F0HEC)xe2x80x99 is put, and next, a based value as xe2x80x981000000(80HEC)xe2x80x99 is put. If it is over the based value, the identifier is put on that position again by one time to ensure the maximum value.
In one embodiment, the data 1 byte of the data information is transmitted as data combined by 8 bit in the non-protocol system.
In a frame structure according to the inventive characteristic, if the data information is the same data as the audio, the video, the control or a user, flag address length information is added between the header information and boundary identification positional information, wherein the flag address length information represents a length of the boundary identification positional information positioned in a data stream by a combination of 8 bits.
In a frame structure according to the inventive characteristic, packet positional information represented as a combination of 8 bits is added between the header information and the boundary identification information length so as to easily search a position of a packet.
In a frame structure according to the inventive characteristic, in case a receiving side requires a re-transmission of the same data, an area between the flags for informing of the start and the completion is provided with the header information which indicates only the required data.
In a frame structure according to the inventive characteristic, in case there is no corresponding data when a transmitting side received a re-transmission demand, an area between the flags for informing of the start and the completion is provided with the header information which indicates information concerned with no-data.
In the inventive frame structure to transmit data, the start and stop flags are defined as digits larger than 128, the header information capable of identifying a nature of data information is provided next to the start flag, the flag data address information is provided next to the header information to successively write address pointers of data restricted to the flag, and data information containing the rest data except data same as the flag is transmitted next to the flag data address information. Meantime, in case that the same data information is transmitted, the header information is more subdivided, a length of the flag data address information and the packet positional information are added so that the receiving side executes more easily the data information search, and overhead data added in the MODEM is eliminated to thereby heighten a transmission efficiency of data per unit time.
Other objects, characteristics and advantages of the invention may be clarified by a detailed description of the preferred embodiments referred to the accompanied drawings.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.